1. Field of the Invention
The invention relates to a device for pneumatically conveying bulk material, especially granular material. The device comprises at least one flow limiter provided within the conveying airstream.
2. Description of the Related Art
In known devices of this kind, the air velocity in the pipelines should not be too low or too high in order to prevent that the conveying action collapses or that the material to be conveyed is damaged and the conveying device is exposed to increased wear. The conveying velocity is affected by several factors, inter alia, pressure loss of the device, the blower output, and the pressure loss caused by the material to be conveyed. In principle, attention must be paid that the blower is as small as possible and as powerful as needed. In this connection, the conduit with the highest pressure loss is used for guidance. In conveying stretches having minimal losses, i.e., relatively short conveying stretches, conveying stretches having minimal height differences and relatively great conduit diameters, the pressure losses must be increased by using apertures as flow limiters in order to prevent an impermissibly high conveying velocity. However, when the pressure loss changes during the conveying process (this can be the case any time when emptying by suction the pipeline after completion of the conveying action), the occurring pressure losses can no longer be compensated by means of the apertures. With decreasing load, the pressure loss also decreases; as a result, the conveying velocity increases. This velocity increase can be easily so high that damage will be caused.